This invention relates to a method of manufacturing a cermet having high toughness and high hardness, and more particularly to a method of manufacturing a cermet of this kind, which exhibits excellent impact resistance and wear resistance when used in cutting tools.
Conventionally, cermets composed mainly of titanium carbide (hereinafter called "TiC" unless otherwise specified) have generally been used as materials for cutting tools. However, since these conventional TiC-base cermets are not satisfactory in respect of toughness, various studies have been made in an attempt to improve the toughness of the TiC-base cermets. In the circumstances, TiC-base cermets which contain titanium nitride (hereinafter called "TiN" unless otherwise specified) have drawn attention because of their improved toughness. It has been recognized that the reason for the improved toughness of such TiC-base cermets containing TiN lies in the fact that TiN acts to restrain the growth of grains in the cermet that would occur during the sintering process. However, in a TiC-base cermet having a high TiN content, the TiN can be decomposed if the green compact is subjected to sintering in a vacuum. The nitrogen gas from the decomposed TiN remains in the sintered cermet and forms pores therein, impeding improvement of the toughness of the TiC-base cermet. Therefore, the maximum possible TiN content in the conventional TiC-base cermets only ranges from 10 to 20 percent by weight (hereinafter percentages of the component elements are weight percentages), and such low TiN content cannot contribute to satisfactory improvement of the toughness of the TiC-base cermet.